#include<stdio.h>
int main(void)
{
	int  num, i, a = 1;
	printf("please input a number\n");
	scanf("%d", &num);
	for (i = 1; i <= num; i++)
	{
		a = a * i;
	}
	printf("%d",a);
    getchar();
    getchar();
	return 0;
}